Method of preparing,maintaining and controlling the supply and consistency of hardfacing slurry



Nov. 18, 1969 J, wooc 3,479,016

METHOD OF PREPARING. MAINTAINING AND CONTROLLING THE SUPPLY AND CONSISTENCY OF HARDFACING SLURRY Filed March 8, 1968 4 Sheets-Sheet l F16: J. l

INVENTOR #625667 J WOOCK A TTUE/K/6V5 Nov. 18, 1969 H. .1. WOOCK 3,479,016

METHOD OF PREPARING, MAINTAINING AND CONTROLLING THE SUPPLY AND CONSISTENCY OF HARDFACING SLURRY Filed March 8, 1968 4 Sheets-Sheet 2 /4 INVENTOR FIG-.2. BY

A 770NCV5 Nov. 18, 1969 H. J. woocK 7 METHOD OF PREPARING, MAINTAINING AND CONTROLLING THE SUPPLY AND CONSISTENCY OF HARDFACING SLURRY Filed March 8, 1968 4 Sheets-Sheet INVENTOR #665667" J WOOCK A 770f/V6K H. J. WOOCK Nov. 18, 1969 METHOD OF PREPARING, MAlN'I'AlNING AND CONTROLLING THE SUPPLY AND CONSISTENCY OE HARDFACING SLURRY Filed March 8, 1968 4 Sheets-Sheet 1 WHEEL-Lug 4 A 77'0ZA/5V5 United States Patent 3,479,016 METHOD OF PREPARING, MAINTAINING AND CONTROLLING THE SUPPLY AND CONSIST- EN CY 0F HARDFACIN G SLURRY Herbert J. Woock, 420 California St., Arcadia, Calif. 91006 Filed Mar. 8, 1968, Ser. No. 711,669 Int. Cl. B28c 7/04; B01f /14 US. Cl. 259-149 30 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the hardfacing of metallic articles with wear resistant coatings, and more particularly to an improved method and technique for preparing, handling, storing and controlling a supply of hardfacing slurry having predetermined characteristics and properties.

It is well known that the service life of metallic components subject to severe wear and abrasion can be greatly prolonged and their efiiciency and effectiveness maintained by coating the surfaces subject to excessive wear with refractory material highly resistant to abrasion. The problems associated with preparing and applying such protective coatings are many and highly frustrating in nature. One of the leading causes of the problems is the fact that the coating materials include ingredients of widely varying specific gravities with the result that these ingredients are constantly tending to stratify. Ingredients having the greatest density and wear-resisting characteristics settle out quickly and therefore must be agitated constantly and violently to prevent this stratification.

Greatly improved equipment and methods of preparing and controlling the consistency of hardfacing slurry over those previously proposed are disclosed in my US. Patents 3,056,383 and 3,056,693 both granted Oct. 2, 1962. These patents disclose means and methods for maintaining the consistency of the hardfacing slurry by continually recirculating the slurry supply by withdrawing portions of the slurry from the bottom of the container and returning it into the top of the main supply. The return flow includes a flow layer of slurry distributed over substantially the entire interior portion of the container side Walls for the purpose of keeping this surface wiped clear of heavier components. Also disclosed in my aforementioned patents are means for sensing the viscosity of the slurry and for adding both water and dry constituents as needed and in the amount necessary to maintain the supply and the consistency of the material within the close tolerance limits required for satisfactory results.

In practice, however, it has been found that superior results to those disclosed in my patents can now be achieved by refinements and additional expedients to be disclosed and claimed herein. In particular, it has been found that precise control and regulation of numerous facets and aspects of the overall method must be taken into account in order to maintain the consistency of the slurry at the proper standards for high-quality uniform results. For example, the viscosity of the slurry must be carefully regulated in order for the slurry to be applied in the desired manner.

The foregoing and many other frustrating problems associated with the preparation and maintenance of a supply of hardfacing slurry are overcome by utilizing the greatly improved technique and methods constituting the present invention.

It is therefore a primary object of the present invention to provide an improved method of preparing and maintaining a supply of hardfacing slurry including as constituents materials of widely differing specific gravities and for keeping these ingredients uniformly dispersed.

Another object of the invention is the provision of an improved method for maintaining a supply of hardfacing slurry and for continually checking the viscosity and adding ingredients of the type and character necessary for maintaining the viscosity substantially uniform at all times.

Another object of the invention is the provision of an improved method for maintaining the ingredient of slurry uniformly dispersed and for flushing the slurry from the circulating ducts for storage between periods of use of the slurry, without removing the slurry from the apparatus.

Another object of the invention is the provision of a method of maintaining a supply of hardfacing slurry generally constant and for adding ingredients thereof in the proper proportions for make-up purposes.

Another object of the invention is the provision of an improved method for continually checking the level of a supply of hardfacing slurry and for adding liquid and solid ingredients as necessary to keep the supply level Within selected upper and lower limits and the proportion of the ingredients substantially constant.

Another object of the invention is the provision of an improved method of preparing and handling a thick creamy supply of hardfacing slurry involving continually withdrawing slurry from a supply body thereof and recirculating it, in part, past an applicating station; in part, in a layer passing over viscosity sensing means; and utilizing another part to sweep the walls of a supply container with a flowing layer of the slurry thereby to disperse heavier ingredients settling into stagnant contact with the container walls.

Another object of the invention is the provision of a novel method of handling hardfacing slurry involving recirculating the supply over a plurality of parallel paths, one of which includes an unrestricted path arranged to sense the pressure of the circulating slurry.

Another object of the invention is the provision of improved means for handling and maintaining a supply of hardfacing slurry featuring a mode of simultaneously varying the pressure prevailing in recirculated slurry and the depth of a layer of the slurry being returned to a supply container in a manner to sweep the walls thereof clear of ingredients tending to collect on the container walls.

Another object of the invention is the provision of an improved method of handling hardfacing slurry featuring the use of a recirculating pump normally to recirculate the slurry and keep the ingredients thereof uniformly dispersed and thereafter enlarging the volume of the pump chamber to receive and store the slurry in stratified condition until the slurry is again needed for application to articles to be protected thereby.

Another object of the invention is to cool the slurry by applying a blast of cool air against a cascading layer thereof.

Another object of the invention is the provision of an improved method of storing the hardfacing slurry having ingredients of widely differing specific gravities with the water constituent floating on top of the solid ingredients while in stored condition and for gradually restoring the mixed condition of the ingredients by rotating impeller means and gradually decreasing the spacing between the impeller and the bottom of the pump chamber.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawings to which they relate.

Referring now to the drawings in which preferred embodiments of the invention are illustrated.

FIGURE 1 is a diagrammatic view showing the slurry handling equipment and the storage chamber in normal non-operating condition together with a schematic of the control components;

FIGURE 2 is a fragmentary vertical sectional view showing details of the handling equipment in a normal operating condition;

FIGURE 3 is a top plan view of the handling apparatus, including certain additional components;

FIGURE 4 is a fragmentary elevational view in section showing components used to control slurry level;

FIGURE 5 is a fragmentary sectional view showing details of the structure used in the method of feeding solid ingredients to the supply container;

FIGURE 6 is a fragmentary view in section on an enlarged scale showing details of the viscosity control components; and

FIGURE 7 is a fragmentary view, partly in section, of means employed in sensing the pressure of slurry while being recirculated.

Referring initially to FIGURE 1, there is shown schematically most of the components used in practicing the invention method of preparing, handling and maintaining a supply of hardfacing slurry. These include an inverted generally conical slurry supply container 10 having a tubular outlet 11 opening into a horizontally-disposed centrifugal pump chamber. This chamber has a housing formed in part by a stationary member 12 and a vertically adjustable cup-shaped member 13. Suitably supported in the pump chamber is a centrifugal pump impeller 14 for pumping slurry into vertical riser tubes 15 opening into a continuous ring manifold 16 encircling the top of container 10.

The slurry supplied to manifold 16 is divided into several different return paths including a tube 18 having its outlet overlying container 10 and effective to circulate slurry to an article to be coated underlying the discharge end of this tube. Another branch 19 leads from the manifold to a viscosity sensing device, and still another branch 20 (FIGURE 7) comprises a flexible tube for discharging slurry against the interior side walls of container 10. Still another major portion of the slurry escape from the lower interior edge 43 of the manifold and flows downwardly over the interior of the supply container in an accurate manner to 'be described in greater detail presently.

Pump impeller 14 is driven through miter gears 22 and spur gears 23 by a variable speed motor 24.

A second motor 25 drives an endless conveyor 26 underlying hopper 27 containing mixed solid ingredients. 28. These flow onto the conveyor which delivers them into the top of container 10 whenever motor 25 is operatmg.

Water is suplied to container 10 through a supply pipe 30 controlled by a normally closed solenoid valve 31. The latter is energized briefly whenever the viscosity sensing device senses a decrease in viscosity below a predetermined value.

Referring now more particularly to FIGURES 2 and 3, it will be understood that the slurry supply container 10 is suitably mounted on a surrounding main frame 34. Distributed about the pump chamber at the bottom of the supply container are a plurality of upright screws having their opposite ends suitably journalled in bearings 36. Each of the screws 35 mates with a stationary nut 37 fixed to the exterior of the cup-shaped pump casing 13 and are driven simultaneously by a reversible .4 motor drive, not shown, to adjust the vertical position of member 13 relative to the stationary casing member 12. The rim portion of member 12 has a close sliding fit with the interior of cup member 13 and is preferably provided with one or more O-ring sealing gaskets 38. Desirably, the seal should be maintained wet for most effective sealing action and to this end the upper side of casing member 12 may be normally flooded with a shallow body of water.

As shown in FIGURE 2, the cup-shaped member 13 of the pump is shown in its elevated position wherein impeller 14 is highly effective in circulating the slurry from the bottom of the container upwardly into manifold 16 by one and preferably several riser tubes 15 communicating with the periphery of the pumping chamber through outlets 40. Risers 15 are preferably equitably distributed about the container and the pump. Manifold 16 is formed in part by a rotatable ring member 42 supported from the stationary portion of the manifold through mating threads 41. The lower edge of adjustable ring 42 is beveled opposite to the inner surface of container 10 to provide a passage 43 through which slurry is distributed for return flow to the main supply. Importantly, this slurry is distributed in a substantially continuously annular layer flowing downwardly along the interior wall of the container. This gravity-actuated layer of slurry is highly effective in maintaining the interior surface clear of non-moving particles and in wiping away any of the heavier ingredients tending to collect and cling to the interior surface of the container. In fact, all surfaces in contact with the slurry are continually subject to the wiping and dispersing action of the recirculating slurry. This feature of the invention method is very important because the heavier ingredients are constantly tending to settle out of suspension and have a pronounced tendency to cling to any surface with which they come into contact. By maintaining a relatively small reserve column of slurry at all times and by keeping this body in relatively rapid recirculation, it is found that any particles having a tendency to stratify are wiped away, entrained in the recirculating stream and dispersed back into suspension. As soon as these ingredients enter the pump, the impeller completes intermixing and dispersal following which the slurry then is quickly elevated into manifold 16 and distributed through the several paths referred to above including the flooding of one portion onto an article being coated.

The proportion of the slurry employed to sweep the interior walls of the container clear is easily regulated by rotating ring 42 in threads 31 to increase or decrease the size of the return gap 43. Adjustment of this ring also serves to adjust the pressure within the manifold and thereby to vary the rate of circulation of the slurry through tubes 18, 19 and 20. As is best shown in FIG- URE 2, the slurry distributing tube 18 discharges slurry onto an article to be coated, such as a harrow disc 45 rotatably supported in any suitable manner with the rim edge overlying container 10 and so inclined relative to the horizontal that the slurry flowing onto its rim is distributed over a desired radial width as the excess drains off and flows back into the main supply. The viscosity of the slurry and the tilt angle of the disc as it is rotated aids in determining the depth of the layer 46 which remains deposited on the disc and is later fused to the base metal in a suitable furnace. Since these details form no part of the present invention, further description is thought unnecessary at this point.

It will be understood that pump impeller 14 is fixed to the lower end of a shaft 48 enclosed in a housing 49 supported in any suitable manner from main frame 34. Bearings 50 for this shaft are suitably supported above the slurry level. Miter gears 22, one of which is fixed to the upper end of shaft 48, are driven from a motor through a shaft 51 supported in housing 52.

Also shown in FIGURE 2 is a cooling air distributing pipe 53 supported from manifold 16 by a bracket 54. The lower end of manifold 53 is provided with one or more air distributing slots 55 arranged to discharge air in close sweeping contact with the slurry layer normally flowing downwardly over the interior surface of the container from the annular slot 43. It will be understood that more than one air distributing manifold may be used if necessary to sweep cooling air in close wiping contact with the returning layer of slurry. Undesirable heat is generated by the forced circulation of the slurry and, if not removed, the slurry becomes warmer and warmer causing its water content to evaporate at an excessive rate and making it diflicult to control the viscosity of the slurry.

Referring now to FIGURE 4, there is shown a pair of electrical probes 57, 58 adjustably supported from their threaded upper ends on a bracket of insulating material 59. Lock nuts 60 are effective to lock the probes in any adjusted height, the general arrangement illustrated in FIGURE 4 being typical and satisfactory. As will be explained in greater detail below, the shorter probe 57 is normally out of contact with the slurry 44 whereas the lower end of probe 58 is normally submerged in the slurry. If the slurry level falls below probe 58, the holding circuit for relay 61 is de-energized and its contactors drop to close a lower set of contacts 62 thereby completing the driving circuit to conveyor motor 25. Conveyor 26 then operates slowly to deliver a shallow layer of dry ingredients 28 from hopper 27 into slurry container 10, the depth of the layer being controlled by an adjustable gate 29 (FIGURE 5) on the hopper outlet. The conveyor continues to operate until the slurry level reaches the lower end of shorter electrode 57 thereby momentarily restoring the circuit through the coil of relay 61. The momentary energization of the relay raises its contactors and restores the holding circuit through the relay provided by probe 58. Conveyor motor 25 is now de-energized until the slurry level again drops below longer probe 58 or until an alternate control circuit to motor 25 is closed as will be described presently.

The components employed in sensing the viscosity of the slurry and the pressure of the recirculating streams thereof will now be described with particular reference to FIGURES 6 and 7. The viscosity device, designated generally 64, includes a supporting bracket 65 secured to the rim of container 10 and pivotally supporting, at its upper end, a beam 66 from pivot pin 67. A counterbalance 68 is adjustably supported on one end of beam 66 and a tear drop 69' is pivotally suspended from the other end on a threaded rod 70. The flexible supply hose 19 for the slurry has a discharge end 71 surrounding stem 70 and adjustable therealong by means of a nut 72. By adjusting this nut along stem 70 the rate of flow of the slurry from the end 71 of the hose over the tear drop can be varied. It is important that a sufficient stream of slurry be delivered onto the tear drop to provide a continuous and unbroken layer covering all areas of the tear drop. Even if the viscosity of the slurry increases it is important that the supply stream flowing thereover be sufl icient to maintain the entire tear drop fully covered with slurry. This is for the reason that if there is a dis continuity in the layer, heavier ingredients tend to settle out along the marginal edges of the stream and are not easily displaced by the flow action of the stream itself even after the proper viscosity has been restored.

Rigidly supported on bracket arm 65 are a pair of normally open micro-switches 74, 75 having their contactors positioned closely to either lateral side of an arm 76 rigid with beam 66. It will therefore be apparent that if beam 66 pivots clockwise switch 74 will be closed whereas, if it swings counterclockwise, switch 75 will be closed. The normally open switch '74 is in circuit with the coil of solenoid valve 31 controlling the supply of make-up water to the slurry whereas switch 75 is in circuit with conveyor drive motor 25. If the viscosity of the slurry is at a proper value the stream flowing over the tear drop has a thickness and weight exactly right to counterbalance weight 68. If the viscosity increases only slightly then the thickness of the layer flowing over tear drop 69 increases thereby counterbalancing beam 66 clockwise whereas if the viscosity decreases the thickness of the layer and therefore the weight of the material on the tear drop decreases allowing the beam 66 to pivot counterclockwise to close the conveyor motor circuit and add solid ingredients to the slurry supply.

To aid the operator in adjusting the speed of the slurry pumping motor 24, the rate of flow of the recirculating slurry over tear drop 69, the coating station at the end of hose 18 and the amount of slurry circulating through gap 43, it is found most advantageous to utilize a device and a method of sensing the pressure of the slurry within the flexible hoses without, however, imposing objectionable restriction on the flow of the slurry. A particularly simple and effective mode of sensing the slurry pressure is to divert a portion of the stream from some part of the recirculating path and sensing its pressure in some intelligible manner.

As herein shown in FIGURE 7 by way of example, this is done by branching off a portion of the flow from hose 19 through flexible tubing 20. The free end of this loop is trained through a copper tube which is in turn welded to bracket 81. A weight 80 is adjustable along slotted arm 81 fixed to shaft 82 pivotally supported on a bracket 83. Also fixed to bracket 81 are a pair of arms 84 to the outer ends of which are connected a flexible cord 85 having one or more turns of its mid-portion wrapped about a spool 86 equipped with a point 87. Spool 86 is rotatably supported at the upper end of a bracket 88 for a calibrated stationary dial 89. It will be evident that the pivotal movement of the rigidly connected arms 81 and 84 serves to rotate spool 86 and point 87 through an arc controlled by the movement of the arms.

Weight 80 on arm 81 is so adjusted as to support the discharge end 90 of hose 20 closely against the slurry flowing downwardly over the interior surface of supply container 10. Normally, end 90 is positioned approximately as shown in FIGURE 7 with the result that the reaction force from the discharging slurry tends to repel end 90 away from the container wall thereby causing arms 81, 84 and cord 85 to rotate pointer 87 clockwise over dial 89. If the pressure of the discharging slurry decreases, the reactive force also decreases thereby allowing hose end 90 to pivot closer to the container surface thereby allowing pointer 87 to rotate counterclockwise and indicate to the operator that there has been a drop in the pressure of the recirculating slurry. If the slurry pressure increases, the pointer is rotated in the opposite direction for self-apparent reasons. It will therefore be understood from the foregoing that the pressure of the recirculating slurry is sensed in major part as a function of the reactive force of the slurry discharging from the end 90 of the flexible hose 20.

OPERATION To place the described apparatus in operation, the user first adjusts the cup-shaped member 13 of the pump casing upwardly to its operating position shown in full lines in FIGURE 2. Water is supplied to the upper side of the stationary casing member 12 to assure an effective fluid seal between parts 12 and 13.

This having been done, the variable speed motor 24 is started and water is added to container 10. Dry material is gradually added as the pump operates to mix and recirculate these ingredients until a supply of slurry 44 having the desired creamy consistency and viscosity is obtained to a level intermediate the lower end of the level sensing probes 57, 58. When the viscosity is at a proper value, acontinuous layer of uniform thickness will cling to a metal surface inclined at an angle to the horizontal, such as that indicated for disc 45 in FIG- URE 2. Likewise when the supporting surface is inclined at the appreciably steeper angle employed for the side walls of container 10, the slurry flows freely over this surface at a rate effective to wipe it clear of any heavier particles. The slurry will also form a complete covering coat for tear drop 69 when the quantity applied to the top of the tear drop is adequate for this purpose. There will also be an adequate flow of slurry supplied through risers to maintain the annular manifold 16 completely filled with slurry under an appropriate low pressure. A portion of this slurry is bled off through tubes 18, 19 and 20 while the remainder is adequate to completely fill the annular slot 43 and maintain the interior side walls of the container completely covered with a flowing stream of the slurry.

The slurry is now ready for use and the portion discharging from tube 18 can be used to coat the surface of articles desired to be protected. The consistency and viscosity of the slurry is such as to provide a layer of uniform thickness on this article, the remainder draining away from the edge of the inclined article and flowing back into the main supply for recirculation.

Impeller 14 supplies vigorous mixing and circulating action for withdrawing an ample quantity of slurry from the bottom of the chamber and forcing it upwardly through risers 15 and the various passages referred to above through which the slurry returns to the top of container 10. Owing to the large capacity of this pumping means and the small reserve supply of the slurry normally maintained in the container, substantially all the slurry is maintained in movement thereby preventing the heavier ingredients from settling out and assuring that any which do will be dispersed back into suspension.

If the viscosity increases or decreases, this changed condition is instantly sensed by the viscosity sensing means 64 which operates to close either switch 74 or 75 to add either water or dry ingredients to the supply in the quantity necessary to restore the viscosity to the proper value.

If the level of the slurry falls below the end of probe 58, the holding circuit for relay 61 through the upper contactor of this relay opens. As the relay becomes de-energized, its lower pair of contacts close and energize the conveyor motor which then supplies additional dry ingredients to the container. After a slight amount of dry material has been added, the increase of viscosity is sensed by tear drop 69 which closes switch 74 and solenoid valve 31 to permit water to flow into the slurry. As the viscosity returns to normal switch 74 opens allowing water valve 31 to close. Usually, however, if the dry material conveyor 26 is operated the water valve will not close until after the slurry level has reached the lower end of probe 57 and re-energized relay 61 thereby opening the conveyor motor circuit and re-establishing the holding circuit for relay 61 by way of its upper contact and probe 58.

When the recirculating slurry is properly adjusted and of the proper consistency, the slurry pressure indicator 87 will be in a particular position relative to the indicia on dial 89. The operator makes note of this position for future use in expediting the resumed operation of the apparatus after a shutdown period.

If the operator wishes to discontinue the use of the apparatus or to stop pump motor 24, he first rotates the screws 35 in a direction to lower pump casing 13. During this operation the pump motor continues in operation. As pump housing 13 is lowered the slurry drains into the pump casing and the heavier ingredients quickly settle and stratify. The water floats on top of the heavier ingredients and is recirculated to flush all parts of the apparatus and of the recirculating circuit clear of any slurry residue following which motor 24 may be stopped. Casing 13 will then be positioned to store all the slurry with the water level below flooding pump impeller 14.

The apparatus may be left in this condition indefinitely and returned to operation very quickly and easily at any time simply by closing the main power switch to restart pump motor 24. The operation of impeller 14 vigorously agitates the water floating on top of the solid material with the lighter components. These are forced upwardly through the apparatus and the several hose passages. Meanwhile, screws 35 are operated to gradually elevate pump casing 13 as the impeller gradually returns more and more of the solid ingredients to circulation despite the very compactly stratified condition of the heavier portions thereof. In a very brief time all the ingredients will have been intermixed and restored to container 10 with major portions continuing to be recirculated. If any of the water has evaporated during the inactive period, the viscosity control quickly senses this and acts automatically to add water as necessary to restore the proper consistency.

While the particular method of preparing, maintaining and controlling the supply and consistency of hardfacing slurry herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention, and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

I claim:

1. The method of controlling the viscosity of a thick creamy slurry of hardfacing materials which comprises:

continuously circulating said slurry to maintain the constituents thereof uniformly dispersed, passing at least a portion of the circulating slurry over a counterbalanced surface to coat the same with a slurry layer having a thickness varying with the viscosity of the slurry,

sensing a change in the weight of the slurry on said counterbalanced surface, and

utilizing the sensed change in the weight of the slurry on said surface to control the addition of one or more of the slurry ingredients as necessary to maintain the viscosity of the circulated slurry at a desired consistency.

2. The method defined in claim 1 characterized in the step of adding a liquid to decrease the weight of the slurry flowing over said counterbalanced surface.

3. The method defined in claim 1 characterized in the step of adding dry ingrenients to said slurry in response to a sensed decrease in the weight of the slurry flowing over said counteibalanced surface.

4. The method defined in claim 1 characterized in the step of adjusting the flow rate of the portion of slurry passing over said counterbalanced surface as necessary to maintain complete coverage of said counterbalanced surface.

5. The method defined in claim 4 characterized in the step of discontinuing the addition of any ingredient to the slurry when the sensed weight of said counterbalanced surface is normal and indicative of the desired viscosity of said slurry.

6. The method of maintaining a slurry of hardfacing constituents of widely differing specific gravities uniformly dispersed and of controlling the flow thereof in several flow paths, said method comprising:

maintaining a main body of said slurry in a conical container,

continuously withdrawing slurry from the bottom portion of said container,

dividing the withdrawn slurry into at least first and second portions,

continually returning slurry from said first portion to the upper portion of said container and there distributing a layer of slurry over substantially the entire interior surface of said conical container as the slurry returns by gravity flow into the main body of the slurry, and

simultaneously varying the thickness of said gravity actuated return layer of slurry to obtain uniform wiping action over substantially the entire interior surface of said conical container.

7. The method defined in claim 6 characterized in the step of varying the rate of withdrawal of slurry from said conical container by utilizing a centrifugal impeller driven at variable speed.

8. The method defined in claim 6 characterized in that the step of distributing slurry from said first portion includes the step of rotating a single ring concentric to the upper rim of said conical container to regulate the flow of said slurry through an annular gap encircling and discharging onto the interior surface of said conical container at a level above the normal level of the main body of slurry in said conical container.

9. The method defined in claim 8 characterized in the step of first adjusting the size of said annular gap through which slurry from said first portion flows, and

thereafter adjusting the speed of the pump to provide the desired pressure to the flowing slurry for proper flooding at all stations.

10. The method defined in claim 6 characterized in the steps of:

bleeding off a third portion of the slurry withdrawn from said conical container,

continually passing slurry from said portion through a movably supported tube and directing the same from the discharge end thereof generally normally onto a rigid surface, and

utilizing the force of the discharging stream of slurry to indicate the flow pressure of the slurry being withdrawn from said conical container.

11. The method defined in claim 10 characterized in the step of sensing the magnitude of the reactive force of the slurry discharging from said tube through movement of said tube and said rigid surface relative to one another, and utilizing the sensed movement of the tube to operate indicator means.

12. The method defined in claim 10 characterized in the step of utilizing a flexible tube having a discharge end free to move toward and away from said rigid surface in response to changes in the discharge of slurry onto said rigid surface.

13. The method defined in claim 12 characterized in the step of positioning the discharge end of said flexible tube to discharge the slurry against an inner portion of said container coated with a layer of slurry from said first portion of slurry and utilizing the latter to carry the slurry discharging from said flexible tube back into the main body of slurry in said conical container.

14. The method of maintaining a supply of hardfacing r slurry formed of constituents of widely differing specific gravities uniformly dispersed and cooled sufiiciently to avoid excessive evaporation of the Water constitutent, said method comprising:

providing a supply of said hardfacing slurry in an inverted conical container,

continually recirculating said supply of slurry to maintain the constituents in suspension by withdrawing slurry from the lower apex end of said conical container and cascading the withdrawn slurry in a layer distributed over substantially the entire inner upper portion of said conical container, and

sweeping said cascading layer with air to carry away heat generated by the recirculation of said slurry.

15. The method defined in claim 14 characterized in that said air sweeping step is carried out by directing a stream of atmospheric air circumferentially of the interior of said conical container with a major portion of the air sweeping over the cascading layer and some air sweeping across the surface of the main supply of slurry in said container.

16. The method of maintaining a supply of electrical conductive hardfacing slurry between selected upper and lower levels which method comprises:

providing a supply of said slurry in a conductive container to a level between an upper and a lower level of said slurry,

supporting a pair of electric probes insulated from one another above said slurry supply with the lower end of a first one thereof terminating at said lower level and the lower end of a second one thereof terminating at said upper level, and

utilizing said probes in an electrical control circuit adapted to be completed and broken via the conductivity of the slurry as the level thereof falls below said first probe and rises above the lower end of said second probe thereby to control the supply of additional solid ingredients of said slurry to said slurry container.

17. The method defined in claim 16 characterized in the steps of:

sensing a change in the viscosity of said slurry supply as additional solid ingredients are added thereto, and utilizing a sensed increase in the viscosity of said slurry to control the addition of water to the slurry until the viscosity thereof returns to a selected value, and thereupon terminating the addition of said water until a lowering of the viscosity is sensed. 18. The method of mixing and storing a supply of hardfacing slurry having ingredients of widely differing specific gravities which method comprises:

providing a hardfacing mixing and storage circuit including an inverted conical container for mixed slurry opening into a variable-volume closed pumping chamber having a slurry discharge arranged to distribute slurry about the interior upper surfaces of said conical container, said pumping chamber being variable between a minimum volume effective to provide for the efficient pumping of slurry from the bottom to the top of said container and a substantially larger volume adequate to store the slurry contents of said container,

normally circulating slurry between the bottom and the top of said container via said pumping chamber to maintain the slurry ingredients uniformly dispersed, and

increasing the volume of said pumping chamber until the slurry in said container has drained into said pump chamber, and

there storing the slurry until there is a demand for slurry.

19. The method defined in claim 18 characterized in the steps of:

remixing the ingredients of said slurry after a period of storage in said pump chamber by resuming pumping of slurry ingredients into the top of said container while decreasing the volume of said pumping chamber toward the said minimum volume thereof.

20. The method defined in claim 19 characterized in the steps of:

discontinuing the decrease in the volume of said pumping chamber when the volume thereof reaches said minimum volume, and

continuing to pump slurry from the bottom to the top of said container to maintain the slurry ingredients dispersed and intermixed.

21. The method defined in claim 20 characterized in the steps of:

utilizing a container of inverted conical shape to store mixed slurry ready for use,

distributing the slurry returned to the top of said conical container in a thin layer substantially covering the interior surfaces thereof, and

utilizing said distributed layer of slurry to wipe the interior surfaces of the container free of slurry ingredients tending to settle into positions of rest on said surface.

22. The method defined in claim 21 characterized in the steps of supporting said impeller means in a fixed plane of rotation closely beneath the top of said pumping chamber, and

varying the volume of said pumping chamber by moving the bottom and peripheral walls thereof vertically between a minimum volume position wherein said bottom wall is spaced closely beneath the bottom of said impeller means and other positions spaced substantially therebelow.

23. The method defined in claim 18 characterized in the steps of:

rotating the impeller means in said pumping chamber to circulate slurry from the bottom to the top of said container.

24. The method of claim 23 characterized in the step of rotating said impeller means selectively at different speeds and as necessary to assure circulation of the slurry at a rate adequate to provide a flowing layer thereof covering the full interior circumferences of said conical container above the level of the main body of slurry therein.

25. The method defined in claim 18 characterized by the steps of forming said pumping chamber with a stationary generally horizontally disposed top wall closely spaced to rotary centrifugal impeller means, and

forming the remainder of said pumping chamber of a vertically adjustable cup-shaped member having a bottom adapted to be positioned closely beneath the lower side of said impeller means when said cupshaped member is elevated to the minimum volume condition of said pumping chamber.

26. The method defined in claim 25 characterized in the step of placing a liquid charge in said cup-shaped member on the upper side of said pumping chamber to aid in forming a seal between the relatively movable members forming said pumping chamber.

27. The method defined in claim 25 characterized in the step of providing a slurry outlet from said pumping chamber leading to the top of said container which slurry outlet is located in the stationary pump chamber member closely overlying said rotary impeller 28. The method of mixing and storing a supply of hardfacing slurry having a water solution of ingredients of widely differing specific gravities which method comprises the steps of:

continually recirculating the intermixed slurry ingredients to keep the same dispersed so long as there is a need for mixed slurry,

draining the slurry into a closed chamber for storage when the slurry is not needed, and

returning the slurry to circulation by gradually bringing the stratified ingredients into contact with rotating impeller means from the top toward the bottom of the stratified ingredients. 29. The method defined in claim 28 characterized in the steps of agitating the upper fluid layers of the stratifying ingredients to form a fluent mixture of slurry of increasing vicosity until all stratified portions have been dispersed throughout the mixture, and

recirculating the slurry through a closed slurry circuit While the stratified ingredients are being remixed together.

30. The method defined in claim 28 characterized in thestep of gradually reducing the volume of the chamber containing the stratified ingredients as the viscosity decreases toward a consistency characteristic of the slurry when all ingredients are uniformly dispersed.

References Cited UNITED STATES PATENTS 3,056,383 10/1962 Woock 11858 3,056,693 10/1962 Woock ll7l02 3,143,777 8/1964 Dietert 259149 3,423,238 1/1969 Weiland 259154 ROBERT W. JENKINS, Primary Examiner U.S. Cl. X.R. 

